Abstract: The optical modulator includes optical modulation units. The plurality of optical modulation units is disposed in parallel on the same substrate. One input waveguide branches off to be connected to the Mach-Zehnder type optical waveguide of each optical modulation unit, and an entire optical waveguide is formed such that outputs from the Mach-Zehnder type optical waveguides are combined and output through one output waveguide. A modulation signal with the same intensity is applied to a modulation electrode of each optical modulation unit. In at least some of the optical modulation units, mechanical structures including the modulation electrodes of the optical modulation units are configured such that an amplitude value of an optical output modulated by the modulation signal of the optical modulation unit is ½n (n is a natural number) of a maximum amplitude value in other optical modulation units.

Abstract: An optical waveguide device that uses a thin substrate having an electro-optical effect and a thickness of 10 ?m or less, in which slab propagation light that is reflected from an end face of the device is removed and thus deterioration in an operational characteristic is suppressed. The optical waveguide device includes: a thin substrate which has an electro-optical effect and thickness of 10 ?m or less, and in which an optical waveguide is formed; and a supporting substrate that is adhered to the thin substrate through an adhesion layer. An antireflective film is formed on a part of a side surface of the optical waveguide device.

Abstract: An optical waveguide device using a thin substrate having an electro-optical effect and having a thickness of 10 ?m or less, in which, even when the thin substrate is adhered to a supporting substrate, breakage of the thin substrate or supporting substrate is suppressed, and performance deterioration such as optical loss due to fine cracks is also suppressed. The optical waveguide device includes a thin substrate, which has an electro-optical effect and a thickness of 10 ?m or less, and in which an optical waveguide is formed, and a supporting substrate that is adhered to the thin substrate through an adhesion layer. A structure is formed in a thin-substrate side surface of the supporting substrate, and the supporting substrate is annealed at a high temperature that is equal to or lower than the Curie temperature after forming the concavo-convex structure and before being adhered to the thin substrate.